Process for improving the adhesion of polyester fibrous material to rubber

ABSTRACT

Polyester fibrous materials are provided which have improved adhesion to rubber. The polyester fibrous materials of this invention are obtained by treating the polyesters in the form of fibers, filaments, yarns or fabrics with halogenated aromatic hydrocarbon at an elevated temperature for a short period of time and then advantageously removing substantially all of the halogenated aromatic hydrocarbon from the treated material. The polyester fibers prepared in accordance with this invention are especially useful as reinforcement for rubber products such as tires, conveyor belts and the like.

United States Patent McCullough 1 Feb. 22, I972 [54] PROCESS FORIMPROVING THE ADHESION OF POLYESTER FIBROUS MATERIAL TO RUBBER [72]Inventor: Robert W. McCullough, Riverside, Conn.

[73] Assignee: Collins and Aikman Corporation, New

York, NY.

[22] Filed: Nov. 4, 1969 [21] Appl.No.: 874,043

[52] US. Cl. ..117/47 A, 117/63, 117/76 T, 117/102 R, 117/102 A, 117/106R, 117/138.8 F, 117/161UD,l17/161UF,117/162 [51] Int. Cl. ..B44d 1/092,B32b 25/08 [58] FieldofSearcli ..117/138.8 F, 138.8 N, 47 A, 117/102 A,102 R, 106R [56] Reterences Cited UNITED STATES PATENTS 2,702,254 2/1955Dowd ..1l7/102RX 3,245,937 4/1966 Wagner ..1l7/l38.8FX

3,383,242 5/1968 Macuraetal 3,447,953 6/1969 Gebauer et al... ..l17/106R 3,515,567 6/1970 Tani et al. ..117/47 A X FOREIGN PATENTS ORAPPLICATIONS 805,525 12/1958 Great Britain .,117/138.8 F

Primary Examiner-William D. Martin Assistant Examiner-Ra1ph l-lusackAttorney-Paul & Paul [57] ABSTRACT 8 Claims, No Drawings PROCESS FORIMPROVING THE ADHESION OF POLYESTER FIBROUS MATERIAL T RUBBER BACKGROUNDOF THE INVENTION 1. Field of the Invention This invention is concernedwith polyester fibers having improved adhesion to rubber and to theprocess for obtaining these fibers.

2. Description of the Prior Art Polyester fibrous materials, for examplepolyethylene terephthalate in fibrous form having high tensile strengthsare waterproof and have excellent heat resistance. Because of theseproperties, the polyester fibers are excellent materials for use asreinforcements for rubber products such as tires, conveyor belts and thelike. The polyester fibers, however, exhibit inherently poor bondingproperties especially with respect to rubber. The techniques andadhesive compositions heretofore used to improve the bonding of otherfibrous materials such as nylon and rayon fibers are ineffective whenused on polyester materials. One of the most widely used compositionsemployed to improve the adhesion of nylon and rayon is a mixture ofalkaline precondensates of resorcinol and formaldehyde. However, thealkaline precondensates when used on polyesters are not effective.

Various methods have been suggested in the prior art to improve thebonding of the polyesters to rubber. Compounds such as polyepoxide andisocyanate derivatives and compositions such as those disclosed inBelgian Pat. No. 688,424 or combinations of these materials with theprior art condensates noted above have been indicated to improvesomewhat the bonding of polyester to rubber. The use of certain of thesematerials requires a multiple-dip process. The polyepoxide andisocyanate derivatives, for example, had to be applied in a first dipand then a resorcinol formaldehyde condensate applied in a second dip.The compositions such as those disclosed in Belgian Pat. No. 688,424 canbe applied in a single dip but are rather expensive to manufacture andtend to stiffen the treated polyester fibers.

The cost of all of the methods suggested in the prior art methods forimproving the bonding were somewhat expensive and the necessity ofemploying multiple-step processes increase both the equipment cost andlabor cost. The increase in adhesion obtained by the prior artprocesses, in addition, was often somewhat marginal.

A further problem of the prior art processes was that the waste from theyarn and fabric production operations could not be salvaged and sold foruse in other textile products since the adhesive coatings adverselyeffected the properties, especially the dyeability of the materials. Thereduction in the value of the scrap materials to some extent increasedthe cost of the final product.

It is an object of the present invention to overcome the aforementionedproblems and difficulties encountered in the prior art.

It is a still further object of this invention to provide polyesterfibers having improved adhesion to rubber.

It is a still further object to provide a process for themanufacturingof polyester fibers having improved adhesion to rubber which isefficient, relatively inexpensive and which does not adversely effectthe properties of the treated fibers.

Other objects and advantages of this invention will become apparent froma further reading of the specification and subjoined claims.

SUMMARY OF THE INVENTION The objects of this invention are achieved bytreating the polyester fibers with a halogenated aromatic hydrocarbon atan elevated temperature for a short period of time and then removing thehalogenated aromatic hydrocarbon from the treated polyester fibers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fibrous materials which aretreated in accordance with the present invention are made from syntheticlinear polyesters which are the condensation polymerization products ofdicarboxylic acids and polyhydric alcohols. The repeating structuralunits of the polymer chain include at least one divalent carbocylic ringcontaining at least six carbon atoms which is present as an integralpart of the polymer chain and have a minimum of four carbon atomsbetween the points of attachment of the ring in the polymer chain. Thepreferred synthetic linear polyesters are of the polyethyleneterephthalate type. Other types of polyesters are likewise employablesuch as those obtained by polymerizing a dicarboxylic acid,bromoterephthalic acid, 4,4-benzophenonedicarboxylic acid and so forthwith glycols such as those of the formula HO(CI-I ),,OH wherein n is awhole number from 2 to 10 such as diethylene glycol, neopentylene glycoland the like.

The polyester fibrous materials when treated in accordance with thisinvention may be in various forms. The polyester fibers may be treatedas continuous filament, or as chopped tow. The fibers may also be spuninto yarns or woven into fabrics and then treated. When referring toyarns, this is intended to include filament yarns, spun yarns, and thelike. The yarns and fabrics that are treated according to this inventionpreferably consist of only polyester fibers. However, it is possible totreat polyesters in blends with other fibers by the present inventionproviding the other fibers are not adversely affected.

The halogenated aromatic hydrocarbons which are employed in the presentinvention may be monocyclic or bicyclic hydrocarbons with the monocyclichydrocarbons being preferred. The halogenated aromatic hydrocarbons arerepresented by the formula R2 wherein R, and R, are the ame" ordifferent and represent hydrogen, an alkyl having one to four carbonatoms such as methyl, ethyl, n-propyl, isopropyl, and n-butyl or analkenyl having two to four carbon atoms such as vinyl, l-propenyl and2-butenyl. When R and R are attached to vicinal carbon atoms they may beattached to each other to form a five-tosix-membered aliphatic oraromatic ring when taken together with the vicinal carbon atoms of thearomatic ring of the compound of Formula I, with the naphthalene ringsystem being the preferred ring system when R and R are joined together,R is a lower alkylene having one to four carbon atoms such as methylene,ethylene, propylene and butylene, or an arylene radical, preferably aphenylene radical such as 1,4-phenylene. The symbol X in the aboveformula stands for a halogen such as fluorine, chlorine, bromine oriodine, n is a whole number from 1 to 3 and when n is two or more X canstand for the same or different halogens and m is a whole number from 1and 2.

The process of the present invention is conducted in either the liquidphase or vapor phase as will be explained later in greater detail.

The halogenated aromatic hydrocarbon employed in the liquid phase methodof the present invention should have a melting point of below C. and bea liquid at the desired treating temperature. The ideal halogenatedaromatic hydrocarbon compounds for employment in the present inventionmelt at a temperature below C. and have a boiling point above C. andmore preferably above 200 C. The halogenated aromatic hydrocarbon shouldbe substantially anhydrous. However, it can contain minor amounts ofwater and will tend to pick up small amounts of water from the polyesterbeing treated. Since the treatment is conducted at elevatedtemperatures, the water is volatilized and removed from the treatingbath.

Formulu l The halogenated aromatic hydrocarbons employed in the vaporphase should vaporize at a temperature below the shrink or decompositiontemperature of the polyester to be treated. The preferred halogenatedaromatic hydrocarbons for employment in this invention should volatilizeat a temperature above 120 C. but below l80200 C.

Blends of halogenated aromatic hydrocarbons can be employed if desired;however, it is preferable to employ a single compound, especially in thevapor-phase method, as it facilitates the separation and recovery of thehalogenated aromatic hydrocarbon as will be more specifically set outbelow.

The preferred halogenated aromatic hydrocarbons for employment in thisinvention are represented by the formula R Formula 11 wherein X ischlorine or bromine and n is a whole number from 1 to 3.

The mono-halogenated compounds wherein R and R are hydrogen, that is themono-halo-benzenes, are especially useful in the vapor-phase method.

The mono-halogenated benzenes are generally not employed in theliquid-phase treating method because of their relatively low boilingpoints but can be employed in the liquid phase if the process isconducted at a temperature below the boiling point or under pressureconditions. Even if the process is conducted at normal pressures,mono-halogenated compounds such as bromobenzene and iodobenzene can beemployed in the liquid process to some advantage.

The dihalogenated benzenes on the other hand, are quite useful in boththe liquid and vapor process of the present invention and are one of thepreferred class of compounds. All of the isomers of the dihalogenatedbenzenes such as the dichloro, the dibromo and diiodo benzenes giveexcellent results. The mixed dihalogenated compounds, such as, mandpbromochlorobenzenes and the iodobromo benzene compounds, such as theortho and meta isomers are likewise useful in the present invention.

The most important class of compounds for employment in the liquidprocess of the present invention are the trihalogenated benzenes. All ofthe isomers of the trichloro benzenes, such as the 1,2,3-trichloro,1,2,4-trichloro and the 1,3,5-trichloro benzenes are the most preferredcompounds for employment in the liquid process. The other trihalogenatedbenzenes, such as the trifluoro, the tribromo and triiodo and thevarious mixed halogen compounds are likewise useful and are also in thepreferred class compounds. The trihalogenated aromatic hydrocarbons arepreferably not employed in the vapor phase because of their higherboiling points.

Of the compounds wherein R, and R represent alkyls having one to fourcarbon atoms, by far the most important class of compounds are thehalogenated toluenes and halogenated xylene compounds, with even themonohalogenated compounds, such as the chlorotoluenes and bromoxylenes,being quite suitable for use in even the liquid-phase method.

Of the compounds wherein R and R are attached to each other to form afive-to-six-membered ring, particular attention is directed to thehalogenated compounds of the naphthalene series such as themonohalogenated naphthalenes and the dihalogenated naphthalenes such asl,2,-dichloro, 1,3- dichloro and l,4-dichloro naphthalenes.

Of the compound where R is a lower alkylene and m is 2, particularattention is directed to compounds such as benzylchloride, achlorotoluene, a-o-dichlorotoluene, bromotoluene and a bromo-o-xylene.

The selection of the particular halogenated aromatic hydrocarbon isdependent on various factors such as the desired treatment temperatures,phase, cost and commercial availability of the compound, and theresulting improvement in the properties of the polyester. By comparingall of these factors, it has been found that the trichlorobenzenes areclearly the preferred compounds for employment in the liquid phasetreatment.

In the method of this invention the synthetic linear polyester istreated with the halogenated aromatic hydrocarbon for a short period oftime at an elevated temperature. More particularly, in the liquid-phasemethod, the polyester is passed through a bath of the halogenatedaromatic hydrocarbon at a temperature of to 200 C. at a speed such thatimmersion time in the halogenated aromatic hydrocarbon is from 10" to 20seconds. Generally, a treatment temperature between C. and C. issufficient in order to obtain the desired improvement in adhesion anddoes not cause shrinkage or degradation of the polyester polymers.Shorter immersion times can be employed. It has been found, however,that about 10 seconds gives the optimum results. Immersion times inexcess of 20 seconds can be employed, but no advantage is obtained withthe longer treatment times.

In the vapor-phase treatment, the polyester material to be treated isfed through a vapor of the halogenated aromatic hydrocarbon. In thepreferred embodiment, the vapor is heated to a temperature where thevapor will condense in a thin film on the polyester which is fed intothe vapor. Since it is most convenient to keep the polyester at roomtemperature before treatment, the vapor should be maintained at atemperature wherein it will condense on the room temperature polyestermaterial. The process can also be conducted by maintaining thetemperature of both the polyester and the halogenated hydrocarbon vaporsufficiently high so that there is no substantial amount ofcondensation. The treatment time should be relatively short with timesof 10" seconds to l() seconds being quite sufficient.

After the treating step, all or substantially all of the halogenatedaromatic hydrocarbon remaining on the polyester fibrous material isadvantageously removed preferably by extraction. The extraction isadvantageously conducted by passing the treated polyester through asolvent with which the halogenated aromatic hydrocarbon is miscible andwhich has a boiling point that is substantially different and preferablylower than the boiling point of the halogenated aromatic hydrocarbon inorder to facilitate the separation and recovery of the materials.Solvents which have proven to be especially valuable as extractionmedium are the halogenated aliphatic hydrocarbons, such as methylenechloride, trichloroethylene, l,l,l-trichloroethane, perchlorethylene andmixtures thereof. The extraction is preferably conducted in a series ofsteps. This is advantageously conducted by passing the treated materialthrough a series of degreasers in which the extraction medium is flowingcounter to the direction of advancement of the treated material. Theextraction medium is then removed by passing the material through aheated zone, for example, an oven or a set of can dryers. Both thehalogenated aromatic hydrocarbon and the extraction medium are thenrecovered, purified and reused.

An alternate method of removing the halogenated aromatic hydrocarbonwhich has proven to be quite satisfactory is to pass the treatedmaterial through a vacuum chamber which causes the treating medium tovolatilize off the polyester. This method is particularly useful whenemploying the vapor-phase treating method.

It should be noted that it is not essential that all of the halogenatedaromatic hydrocarbon be removed from the polyester material aftertreatment. Some of the halogenated aromatic hydrocarbon treating agentmay be entrapped in the fibrous structure during treatment. The amountof entrapped treating agent can be as high as 5-10 percent based on theweight of the fiber without adversely effecting the adhesion propertiesof the treated polyester material. However, it should be noted that allof the treating agent which is on the surface of the fiber or which canbe simply removed by solvent extraction or vacuum extraction should beremoved in order to prevent formation of blisters in the final productwhen the product is subjected to elevated temperature.

The treated polyester, whether in the form of fiber, yarn or fabric,after treatment, shows a substantial improvement in the degree ofadhesion of the polyester fibers to rubbers. In addition, the otherdesirable properties such as tensile strengths are not adverselyeffected. 1n particular, it should be noted that the flexibility of thetreated material is not altered. A further advantage of this process isthat the scrap material can be reclaimed and reused in other textileproducts. Most of the properties of the reclaimed fiber are similar tothose of the virgin material with the dyeability being substantiallyimproved. It can readily be seen from the above disclosure that theprocess of the present invention requires a minimal amount of relativelyinexpensive materials and the process is rapid requiring a minimalamount of labor.

The treated polyester fibers can be used as reinforcements for varioustypes of rubbers, such as natural rubber, styrenebutadiene rubber,acrylonitrile-butadiene rubber, polybu- -tadiene rubber, polyisoprenerubber and polychloroprene rubber. The rubber composition can containthe usual additive such as fillers, vulcanizing agents, acceleraters forcuring, softners and antioxidants.

The treated polyester fiber, yarns and fabric can be used without anyprecoating as is required in the prior art. The results obtained arequite satisfactory with increases in bond strength of -100 percent beingreadily obtained. If desired,

the polyester materials can be precoated with a bonding assistance suchas the resorcinol formaldehyde derivatives noted above. The precoatingis especially useful when the reinforcement material is comprised of ablend of polyester fibers with another fiber such as nylon. In order toinsure maximum contact between the polyester fibers and rubbercomposition, the polyester can be coated with a thin coating of a rubberlatex. It should be noted, however, that precoating is optional and isnot required in order to obtain improved adhesion.

The fibrous polyester material can be used as reinforcement for rubbermaterial by casting the uncured rubber composition about the polyesterfibrous material andthen vulcanizing the rubber composition. Thepolyester can also be used as a reinforcement between cured rubbersections by using an adhesive which causes a solvent softening of therubber compositions with a resultant adhesion between the rubbermaterials. Other similar methods can of course be employed.

The following examples are given by way of illustration and not intendedto limit the scope of the subjoined claims. All percentages are percentsby weight, not percent by volume, unless otherwise noted.

EXAMPLE l Ten gram skeins of LOGO-denier polyethylene terephthalate tirecord (commercially known as Encron) were prepared. The skeins were cutin half. One half of the skein was retained as the untreated sample. Theother half of the skein was treated in accordance with the presentinvention by passing the yarn through a bath of the halogenated aromatichydrocarbon for the time and at the temperature noted below. Each samplewas solvent extracted with perchloroethylene and All samples weremeasured before and after treatment and there were no significantchanges in either length, tensile strength or flexibility. There was aslight increase in the weight of the samples in order of 0.05-1.25percent based on weight of the untreated material adjusted for loss ofspinning lubricams and moisture.

' EXAMPLE 2 Example 1 was repeated with the exception that the samplewas treated with the below-noted halogenated aromatic hydrocarbons atthe times and temperatures noted below.

Halogenated Aro- Time Temperature Sample matic Hydrocarbon Sec. C.

a monochlorobenzene 10 1 b monochlorobenzene 1 c monochlorobenzene 10180 d 1,2-dich1orobenzene 5 200' e 1,3-dich1orobenzene 5 200 fa-o-dichlorotoluene 1O 180 g p-fluorotoluene 5 180 All samples weremeasured before and after treatment and there were no noticeable changesin tensile strength, length or flexibility.

EXAMPLE 3 Test blocks were prepared by adhering one treated yard and oneuntreated yarn to a block of tire rubber with a hot path.

The rubber of the tire patch was vulcanized and the yarn was pulled fromthe test block using a Suter single-strand tester.

In order to determine the bond properties of the treated polyester whencemented between two rubber surfaces, a rubber patch was adhered to asecond vulcanized rubber block with a resorcinol formaldehyde adhesiveafter a treated and untreated yarn were placed between the rubber patchand rubber block. The yarns were then pulled from the rubber sample witha Suter single-strand tester. The result of the test EXAMPLE Samples ofyarn treated in accordance with Examples la-l g and -23 were embedded inan uncured polychloroprene rubber in cylindrical molds 1 /2 inches highand one-half inch in diameter. Samples of untreated yarn were embeddedin similar molds. The polychloroprene rubber was cured at roomtemperature for 96 hours in accordance with the manufacturer'sinstructions..

When it was attempted to remove the treated polyester from the mold, theyarn samples broke and did not release from the rubber. The untreatedyarn was pulled from the samples with an average of 9.8 lbs.

What is claimed is:

1. The process for improving the adhesion of a synthetic linearpolyester fiber to rubber comprising contacting said polyester fiber ata temperature of l20-200 C. for l0' -20 seconds with a member selectedfrom the group consisting of (a) a halogenated aromatic hydrocarbon ofthe formula iodine, n is a whole number from l to 3 and when n is morethan 1, X stands for the same or different halogens and m is a wholenumber from 1 and 2 and (b) mixtures of said halogenated aromatichydrocarbons and thereafter removing all or substantially all of saidhalogenated aromatic hydrocarbon from said polyester fiber.

2. The process according to claim 1 wherein contacting comprisesimmersing said polyester fiber in a liquid bath of said halogenatedaromatic hydrocarbon.

3. The process according to claim 2 wherein said halogenated aromatichydrocarbon is trichlorobenzene.

4. The process according to claim 2 wherein said halogenated aromatichydrocarbon is extracted from said polyester fiber by a solvent which ismiscible with said halogenated aromatic hydrocarbon.

5. The process according to claim 1 wherein said polyester fiber iscontacted with said halogenated aromatic hydrocarbon in the vapor phase.

6. The process according to claim 5 wherein said halogenated aromatichydrocarbon is heated to a temperature below the shrink or decompositiontemperature of said polyester fiber.

7. The process according to claim 6 wherein said halogenated aromatichydrocarbon and said polyester fiber differ in temperature such that thehalogenated aromatic hydrocarbon vapor condenses on said polyester fiberduring treatment.

8. The process according to claim 7 wherein said halogenated aromatichydrocarbon is a member selected from the group consisting ofmonohalobenzene and dihalobenzene.

2. The process according to claim 1 wherein contacting comprisesimmersing said polyester fiber in a liquid bath of said halogenatedaromatic hydrocarbon.
 3. The process according to claim 2 wherein saidhalogenated aromatic hydrocarbon is trichlorobenzene.
 4. The processaccording to claim 2 wherein said halogenated aromatic hydrocarbon isextracted from said polyester fiber by a solvent which is miscible withsaid halogenated aromatic hydrocarbon.
 5. The process according to claim1 wherein said polyester fiber is contacted with said halogenatedaromatic hydrocarbon in the vapor phase.
 6. The process according toclaim 5 wherein said halogenated aromatic hydrocarbon is heated to atemperature below the shrink or decomposition temperature of saidpolyester fiber.
 7. The process according to claim 6 wherein saidhalogenated aromatic hydrocarbon and said polyester fiber differ intemperature such that the halogenated aromatic hydrocarbon vaporcondenses on said polyester fiber during treatment.
 8. The processaccording to claim 7 wherein said halogenated aromatic hydrocarbon is amember selected from the group consisting of monohalobenzene anddihalobenzene.